draft release notes for Scala 2.12.11

release-notes-2.12.11.md

Collections fixes

• Fix 2.12-only bug where some toX methods could expose the underlying mutability of a ListBuffer-generated collection (#8674)

(The release includes other collections bugfixes, but this one is especially notable.)

Java interoperability

Assorted small improvements to handling of Java sources (thanks @hrhino).

JDK compatibility

• Make optimizer work on JDK 13+ (#8676)
• Make :javap work in the REPL on JDK 9+ (#8400)

REPL changes

• Improve -Yrepl-class-based (#8712)
• -Yrepl-use-magic-imports avoids nesting $iw wrappers (#8576)

(TODO need much better descriptions)

reflection

• further improved thread safety of runtime reflection (#8433) and fixed a memory leak introduced in 2.12.10 (#8470)

performance

• assorted compilation performance improvements
  • (need an overall compiler benchmark number from Jason)
• assorted collections performance improvements

standard library changes

• Duration strings now support "m" for minutes and "hr" for hours (#8325, #8450)

compiler plugins changes

• -Xpluginsdir works again (it regressed in 2.12.9) (#8542)
• compiler phase ordering is now deterministic in more cases (#8427)

changes relevant to build pipelining (?)

• Add a mode to write separate .sig files without really private members (#8556)

todo: mention scala/scala-dev#675